Web Service Engine Errors

Web Service Engine Errors

To review, web services are not much more than sockets conveying specific information. A web service request and response involves these parts:

1. Client opens a socket to the server
2. Client formats an XML document
3. Client sends the XML content over the socket
4. Server recieves the XML content over the sockedt
5. Server parses the content
6. Server formats XML response content
7. Server sends the response XML content over the socket
8. Client recieves the XML response content over the socket
9. Client parses the XML response content

Platform-specific code on both the client and server sides must both format and parse the XML requests and responses. XML construction and parsing is itself a very detailed operation involving the potential for may problems. The server side adds additional "web service engine" complexity in order to determine which application must be invoked to handle each web service request.

Given this, a wide range of XML parser and web service engine errors can occur. These include, but are not limited to:

• XML is not formatted properly
• Missing required XML content
• XML buffer overflow
• Requested web service not defined

Most of the time, the error is conveyed within the XML response itself. How your particular platform handles errors like this is dependent on the platform, and is the responisibility of the client programmer to understand the platform's behavior. An example of how the XML response will appear is shown below:

Note that errors such as the one above are generated within the web service engine on the server side, and do not involve the actual web service application at all. For example, had the above error been generated in result to a call to GetVehicleInfo, the actual GetVehicleInfo code had not yet been invoked when the error was generated and returned!